Influences of Plasma Plume Length on Structural, Optical and Dye Degradation Properties of Citrate-Stabilized Silver Nanoparticles Synthesized by Plasma-Assisted Reduction

Citrate-capped silver nanoparticles (<i>Ag@Cit NPs</i>) were synthesized by a simple plasma-assisted reduction method. Homogenous colloidal <i>Ag@Cit NPs</i> solutions were produced by treating a <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi mathvariant="normal">A</mi><mi mathvariant="normal">g</mi><mi mathvariant="normal">N</mi><msub><mi mathvariant="normal">O</mi><mn>3</mn></msub></mrow></semantics></math></inline-formula>-trisodium citrate-deionized water with an atmospheric-pressure argon plasma jet. The plasma-synthesized <i>Ag@Cit NPs</i> exhibited quasi-spherical shape with an average particle diameter of about 5.9−7.5 nm, and their absorption spectra showed surface plasmon resonance peaks at approximately 406 nm. The amount of <i>Ag@Cit NPs</i> increased in a plasma exposure duration-dependent manner. Plasma synthesis of <i>Ag@Cit NPs</i> was more effective in the 8.5 cm plume jet than in the shorter and longer plume jets. A larger amount of <i>Ag@Cit NPs</i> were produced from the 8.5 cm plume jet with a higher pH and a larger number of aqua electrons, indicating that the synergetic effect between plasma electrons and citrate plays an important role in the plasma synthesis of <i>Ag@Cit NPs</i>. Plasma-assisted citrate reduction facilitates the synthesis of <i>Ag@Cit NPs</i>, and citrate-capped nanoparticles are stabilized in an aqueous solution due to their repulsive force. Next, we demonstrated that plasma-synthesized <i>Ag@Cit NPs</i> exhibited a significant degradation of methylene blue dye.